1. Field of the Invention
The present invention relates to a multilayer ceramic electronic device greatly reducing the equivalent serial inductance (ESL), more particularly relates to a multilayer ceramic electronic device suitable for a multilayer ceramic capacitor used as a decoupling capacitor.
2. Description of the Related Art
In recent years, while advances have been made in reducing the voltage of power sources used for supplying power to large-scale integrated circuits (LSI""s) and other integrated circuits, the load current has increased.
Therefore, it has become extremely difficult to keep fluctuations in the power source voltage to within tolerances when faced with sharp changes in the load current. Therefore, as shown in FIG. 8, a for example two-terminal structure multilayer ceramic capacitor 100 called a xe2x80x9cdecoupling capacitorxe2x80x9d is now being connected to a power source 102. At the time of transitory fluctuation in the load current, current is supplied from this multilayer ceramic capacitor 100 to the LSI 104 of the central processing unit (CPU) etc. to suppress fluctuation of the power source voltage.
Along with the increasingly higher operating frequencies of today""s CPU""s, however, the fluctuations in the load current have become faster and larger. The ESL of the multilayer ceramic capacitor 100 itself, shown in FIG. 8, now has a great impact on fluctuations of the power source voltage.
That is, in a conventional multilayer ceramic capacitor 100, since the ESL is high, fluctuation of the power source voltage V easily becomes greater in the same way as above along with fluctuations in the load current i shown in FIG. 9.
This is because the fluctuations in voltage at the time of transition of the load current are approximated by the following equation 1 and therefore the level of the ESL is related to the magnitude of fluctuation of the power source voltage. Further, from equation 1, reduction in the ESL can be said to be linked with stabilization of the power source voltage.
dV=ESLxc2x7di/dtxe2x80x83xe2x80x83(1)
where,
dV is transitory fluctuation of voltage (V),
i is the fluctuation of current (A), and
t is the time of fluctuation (sec).
FIG. 10 shows a conventional multilayer ceramic capacitor. In this capacitor, ceramic layers 112A provided with two types of internal conductors 114 and 116 shown in FIG. 11A and FIG. 11B are alternately stacked to form a dielectric body 112. These internal conductors 114 and 116 are formed in a manner led out to the two facing side surfaces 112B and 112D of the dielectric body 112.
Further, in a multilayer ceramic capacitor of such a structure, as a general technique for reducing the ESL, as shown in FIG. 10, a structure setting the ratio of dimensions between a dimension L and dimension W of the external dimensions of the multilayer ceramic capacitor to L/W less than 0.75 has been proposed. In this structure, the path of the current is shortened and the inductance of the internal conductors 114 and 116 is reduced by placing terminal electrodes 118 and 120 at the large area side surfaces 112B and 112D. In this structure, however, there are limits in the production and mounting of the multilayer ceramic capacitor and the inductance cannot be sufficiently reduced.
Note that here, the xe2x80x9cdimension Lxe2x80x9d is the distance between the side surfaces 112B. and 112D of the dielectric body 112 to which the two types of internal conductors 114 and 116 are led out, while the xe2x80x9cdimension Wxe2x80x9d is the distance between the side surfaces 112C and 112E orthogonal to the side surfaces 112B and 112D of the dielectric body 112 to which the internal conductors 114 and 116 are led out.
An object of the present invention is to provide a multilayer ceramic electronic device able to greatly reduce the ESL.
To attain the above object, there is provided a multilayer ceramic electronic device comprising a dielectric body formed by stacking a plurality of dielectric sheets; two types of internal conductors arranged inside the dielectric body sandwiched between the dielectric sheets, formed with lead parts led out straddling three side surfaces of the dielectric body, and interposed between different layers; and two terminal electrodes each arranged at an outer surface of the dielectric body straddling three side surfaces of the dielectric body, connected to one of the two types of internal conductors, and insulated from the other.
According to the multilayer ceramic electronic device of the present invention, two types of internal conductors are alternately arranged in the dielectric body formed by stacking a plurality of dielectric sheets in a manner sandwiched between the dielectric sheets. These two types of internal conductors are led out straddling three side surfaces of the dielectric body. Further, two terminal electrodes are arranged at the outside of the dielectric body straddling three side surfaces of the dielectric body. Each of these two terminal electrodes is connected to one of the two types of internal conductors.
Therefore, by the connection of the two terminal electrodes and two types of internal conductors straddling the three side surfaces of the dielectric body, there are locations in the two types of internal conductors where current flows in reverse directions.
Therefore, an action arises canceling out the magnetic field at the locations where the current flows in reverse directions. Along with this, the effects arise that the parasitic inductance of the multilayer electronic device itself can be reduced and the ESL is reduced.
That is, according to the multilayer ceramic electronic device according to the present invention, a great reduction in the ESL of the multilayer ceramic electronic device is achieved, fluctuation of the power source voltage can be suppressed, and a device suitable for use as a decoupling capacitor can be obtained.
Preferably, lead parts of the two types of internal conductors led out to the side surfaces of the dielectric body are arranged straddling three side surfaces of the dielectric body in a positional relationship not overlapping when projected in a stacking direction of the dielectric sheets.
In this case, the two terminal electrodes can be reliably arranged at the outside of the dielectric body straddling three side surfaces of the dielectric body without short-circuiting with each other.
Preferably, the dielectric body is formed shaped as a rectangular parallelopiped. By making the dielectric body a rectangular parallelopiped in shape, the dielectric body can be easily made and the productivity improved.
Preferably, each of the internal conductors has an internal conductor body portion having a shape matching an outer shape of the dielectric sheet and separated from edges of the dielectric sheet and a lead part formed integrally with the internal conductor body portion on the same plane and led out straddling adjoining three side surfaces of the dielectric body.
Preferably, pluralities of the two types of internal conductors are arranged in the dielectric body.
Preferably, the two types of internal conductors are alternately arranged in the dielectric body.
By arranging pluralities of the two types of internal conductors in the dielectric body, not only does the electrostatic capacity become higher, but also the action of canceling out the magnetic field becomes further greater, the inductance is more greatly reduced, and the ESL is further reduced.
Preferably, lead parts of the internal conductors are arranged straddling a short side surface of the rectangular parallelopiped shaped dielectric body and two long side surfaces positioned at the two sides of the short side surface.
Preferably, matching with the led out shapes of the lead parts of the internal conductors, the terminal electrodes are arranged straddling a short side surface of the rectangular parallelopiped shaped dielectric body and the two long side surfaces positioned at the two sides of the short side surface.
Preferably, lead parts of the internal conductors are arranged straddling a long side surface of the rectangular parallelopiped shaped dielectric body and the two short side surfaces positioned at the two sides of the long side surface.
Preferably, matching with the led out shapes of the lead parts of the internal conductors, the terminal electrodes are arranged straddling a long side surface of the rectangular parallelopiped shaped dielectric body and the two short side surfaces positioned at the two sides of the long side surface.